I run it with SLI and have no issues, however I'm not a BF player so I'm probably not a great example.
On another note, I have killed my RAT RMA-ing for a bad right mouse button (Sticks when i click) Gotta give MadCatz props tho, they have been really great about the whole RMA process

Mine is more than just gaming, the GPU usage just jumps between 2 values back and forth like this. Only way I fixed it was to disable SLI and re-enable every time. Problem persisted with different drivers and cards

My girlfriend wants to buy me a new mouse for Xmas. Currently have a limited edition Logitech G5 mouse.

Love my current mouse but I feel I need a change. I'm stuck between the Cyborg R.A.T. 7 and Roccat Kone +.

Are there any suggestions to sway me in a direction?

Also, and most importantly, are there any knows issues with the Cyborg R.A.T. series mice? Sensor, firmware, driver, DOAs, tendencies to break/brick easily, design, actual function and any other issues?

If you do a little bit of research you'll find quite a few people that had problems with the laser. While some of the problems got fixed in the new version (no difference in name, the ones you can buy now should all come with the fix) other remained like a poor z-tracking.
RMA'ing is very easy and uncomplicated, they don't try to blame you for everything.